package org.eclipse.aether.util.repository;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   * 
   *  http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import java.util.Arrays;
  import java.util.Map;
  import java.util.Objects;
  
  import static java.util.Objects.requireNonNull;
  
  import org.eclipse.aether.repository.Authentication;
  import org.eclipse.aether.repository.AuthenticationContext;
  import org.eclipse.aether.repository.AuthenticationDigest;
  
  /**
   * Authentication block that manages a single authentication key and its secret string value (password, passphrase).
   * Unlike {@link StringAuthentication}, the string value is kept in an encrypted buffer and only decrypted when needed
   * to reduce the potential of leaking the secret in a heap dump.
   */
  final class SecretAuthentication
      implements Authentication
  {
  
      private static final Object[] KEYS;
  
      static
      {
          KEYS = new Object[16];
          for ( int i = 0; i < KEYS.length; i++ )
          {
              KEYS[i] = new Object();
          }
      }
  
      private final String key;
  
      private final char[] value;
  
      private final int secretHash;
  
      SecretAuthentication( String key, String value )
      {
          this( ( value != null ) ? value.toCharArray() : null, key );
      }
  
      SecretAuthentication( String key, char[] value )
      {
          this( copy( value ), key );
      }
  
      private SecretAuthentication( char[] value, String key )
      {
          this.key = requireNonNull( key, "authentication key cannot be null" );
          if ( key.length() == 0 )
          {
              throw new IllegalArgumentException( "authentication key cannot be empty" );
          }
          this.secretHash = Arrays.hashCode( value ) ^ KEYS[0].hashCode();
          this.value = xor( value );
      }
  
      private static char[] copy( char[] chars )
      {
          return ( chars != null ) ? chars.clone() : null;
      }
  
      @SuppressWarnings( "checkstyle:magicnumber" )
      private char[] xor( char[] chars )
      {
          if ( chars != null )
          {
              int mask = System.identityHashCode( this );
              for ( int i = 0; i < chars.length; i++ )
              {
                  int key = KEYS[( i >> 1 ) % KEYS.length].hashCode();
                  key ^= mask;
                  chars[i] ^= ( ( i & 1 ) == 0 ) ? ( key & 0xFFFF ) : ( key >>> 16 );
              }
          }
          return chars;
      }
  
     private static void clear( char[] chars )
     {
         if ( chars != null )
         {
             for ( int i = 0; i < chars.length; i++ )
             {
                 chars[i] = '\0';
             }
         }
     }
 
     public void fill( AuthenticationContext context, String key, Map<String, String> data )
     {
         requireNonNull( context, "context cannot be null" );
         char[] secret = copy( value );
         xor( secret );
         context.put( this.key, secret );
         // secret will be cleared upon AuthenticationContext.close()
     }
 
     public void digest( AuthenticationDigest digest )
     {
         char[] secret = copy( value );
         try
         {
             xor( secret );
             digest.update( key );
             digest.update( secret );
         }
         finally
         {
             clear( secret );
         }
     }
 
     @Override
     public boolean equals( Object obj )
     {
         if ( this == obj )
         {
             return true;
         }
         if ( obj == null || !getClass().equals( obj.getClass() ) )
         {
             return false;
         }
         SecretAuthentication that = (SecretAuthentication) obj;
         if ( !Objects.equals( key, that.key ) || secretHash != that.secretHash )
         {
             return false;
         }
         char[] secret = copy( value );
         char[] thatSecret = copy( that.value );
         try
         {
             xor( secret );
             that.xor( thatSecret );
             return Arrays.equals( secret, thatSecret );
         }
         finally
         {
             clear( secret );
             clear( thatSecret );
         }
     }
 
     @Override
     public int hashCode()
     {
         int hash = 17;
         hash = hash * 31 + key.hashCode();
         hash = hash * 31 + secretHash;
         return hash;
     }
 
     @Override
     public String toString()
     {
         return key + "=" + ( ( value != null ) ? "***" : "null" );
     }
 
 }